Rod anchoring means



Sept. 1969 v H. o. DOHMEIER 3,464,308

ROD ANCHORING MEANS Filed March 5, 1968 s T-NVe-NT K N Hmvs OTfo Define/El FIG. 2. 9 w

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United States Patent 3,464,308 ROD ANCHORING MEANS Hans 0. Dohmeier, 30 Van der Merwe St., Hillbrow, Johannesburg, Transvaal, Republic of South Africa Filed Mar. 5, 1968, Ser. No. 710,565 Claims priority, application Republic of South Africa, Mar. 8, 1967, 67/1,331 Int. Cl. F16b 37/00, 17/00, 39/22 US. C]. 8532 1 Claim ABSTRACT OF THE DISCLOSURE The invention is concerned with a method and means of holding a rod under tension wherein a metal anchoring plate having a perforation therethrough is located around the rod against a rigid surface and the tension applied to the rod in a manner causing deformation of the plate to lock the walls of the perforation onto the rod and retain it under the applied tension.

This invention relates to roof bolts and the like which are generally used in underground mining operations.

Although the invention will be described as applied to roof bolting operations in mines it will be understood that it is equally applicable to other similar operations. It has in fact application in various circumstances where a rod is to be held under tension with one end of the rod projecting through a rigid surface.

Roof bolts are used in large numbers in underground mining operations and numerous different types and designs for such roof bolts have been evolved. However, all these various roof bolts have a shank which is screw threaded at least the end adapted to protrude from a rock face and are secured in position by means of a nut screwed onto the thread, a metal washer normally being present between the nut and the rock face. This is the equipment which has been in use for very many years.

Screw threading operations and nuts are costly relative to the overall price of a roof bolt and it is the object of this invention to provide a method and means for securing roof bolts and the like without the use of the nuts above referred to. From this it will be clear that the invention can be used in many circumstances where a bolt and nut is used and where the bolt need not be screw threaded.

The invention also provides a rod anchoring metal plate having a centrally perforated deformable concave portion in which the central perforation has a wall shaped to lock onto a rod upon deformation of the deformable portion.

The invention also provides a method of anchoring a rod under tension Where one end of the rod projects through a rigid surface comprising placing onto the outwardly extending end of the rod a centrally perforated deformable metal anchoring plate, applying tension to the bolt against said plate to deform it to grip the rod with the wall of the perforation and hold it fast under the tension applied.

Further features of the invention provide for the shaped wall of the aperture through the plate to have a serrated form, for the plate to have short slits extending outwardly from the perforation and for the metal plate to be in the form of a circularly dished plate with three outwardly extending limbs.

A preferred embodiment of this invention will be described with reference to the accompanying drawings and as applied to the anchoring of a mine roof bolt.

In the drawings:

FIG. 1 is a perspective view of a preferred form of plate, and

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FIG. 2 shows a section through an anchored roof bolt assembly with the original outline of the plate shown in dotted lines.

The metal anchor plate 1 shown in FIG. 1 has a centrally dished portion 2 with a perforation 3 through the apex of the dished portion 1 as shown. The wall of the aperture has a screw thread or similar serrated formation 4 formed therein and three equally spaced radial slits 5 extend from the perforation 3 to terminate in smaller holes 6.

symmetrically located between the slits 5 are formed upstanding ribs 7 which give rigidity to the plate in these areas which ensures that with a load applied centrally to the plate the portions adjacent the perforation 3 will bend in a predetermined manner for the purpose more fully set out below.

Aligned with the ribs 7 and extending outwardly from dished portion 2 are three tongues 8 of the plate material forming a stable rock contacting base for the plate. The outer edges 9 of the plate are preferably bent slightly upwardly to facilitate movement of the tongues on the rock surface.

The dished portion is made such that for the usual W diameter anchor rod the highest portion of the dish will be about &5" above the base. The plate is made of high tensile strength steel of a thickness of 7 Similar proportions should be maintained for other diameter anchor boltsbut circumstances may dictate that these be varied.

The plate is made by punching cropping, and screw threading the aperture and pressing out the dished portion. These operations can be performed with the plate cold.

The use of the plate is illustrated in FIG. 2 of the drawings.

As shown the plate 1 is placed over an outwardly extending end 9 of a roof bolt 10 which is situated in a hole 11 in a rock face with the convex surface of the plate 1 outermost. It will be understood that the perforation 3 in the plate 1 should not be much smaller in diameter, say than the W diameter of the roof bolt to be secured. A tensioning deviceis then applied to the end 9 of the bolt to engage the plate near the centre. A tension is then applied to the bolt 10, the expansion unit 12 of the bolt 10 engages the wall of the hole 11 and, as the tension increases, the plate 1 deforms inwardly this causing the central hole 3 therein to diminish in size and the sharp edges 4 thereof to bite into the shank 9 of the bolt. The tensioning device may then be removed and the bolt is held in tension by the plate 1 tending to revert to its normal position.

It will be appreciated that the method and means provided by this invention are preferably used with roof bolts which have no screw threads at all thus obviating the need for any screw threading operations on a bolt shank or the provision of any nuts. In such a combination the shanks of the roof bolts could be made from ordinary roof bolt steel or from steel reinforcing rods of the appropriate diameter, which reinforcing is much used in the building and civil engineering trades and is relatively cheap. The expansion unit 12 will also preferably include means for providing an initial lock to the rock engaging parts thereof.

The usefulness of this invention is further emphasised by the fact that it enables roof bolts already in position in mines and the outer threads of which have been stripped, to be made functional again.

It will thus be appreciated that the invention provides an inexpensive, eflicient and very useful method and means for securing roof bolts in position and also has the effect of making roof bolts themselves cheaper to manufacture.

What I claim as new and desire to secure by Letters Patent is:

1. A rod anchoring metal plate having a deformable concavo-convex portion, a central circular opening through the concave-convex portion and screw thread formations on the wall surface of the opening adapted to bite into and lock the smooth surface of a rod inserted through the opening on deformation of the concavoconvex portion, three slits being provided equidistantly spaced apart and extending radially from the opening through part of the concavo-convex portion of the plate and each terminating in an enlarged opening, three ribs of substantially uniform width being pressed from the plate to project slightly above the convex surface of the plate, these ribs being symmetrically disposed with respect to the slits in the space therebetween and extending radially from the central opening part way only along the concave-convex portion of the plate, but to a greater radial extent than said slits, the inner end of each rib spanning substantially one-third the circumference of said circular opening and said slits providing independent flexing of the inner end portion of the ribs.

References Cited UNITED STATES PATENTS 2,383,164 8/1945 Ryder 85-36 2,748,594 6/ 1956 Edwards. 2,754,717 7/1956 Becker 85-36 2,822,712 2/1958 Garman 85-36 3,226,934 1/ 1966 Emery. 3,215,024 11/1965 Brilmyer et a1. 85-7 15 EDWARD c. ALLEN, Primary Examiner U.S. Cl. X.R. 85-36; 151-38 

